Multi-Scale\nDynamic Modeling of Radial Flow Fixed\nBed Contactors for CO<sub>2</sub> Capture Using a Functionalized Metal–Organic\nFramework

For solid sorbent-based postcombustion CO<sub>2</sub> capture,\nthe contactor technology plays a crucial role in achieving the desired\nlevel of technical and economic performance. In this work, radial\nflow fixed bed (RFFB) contactor technology is investigated. These\nbeds offer considerably lower pressure drop compared with conventional\naxial flow fixed bed technology. Furthermore, they offer many possible\noptions for flow configurations that can be exploited during cycle\ndesign to achieve the high potential of a sorbent. A functionalized\nmetal–organic framework (MOF) that exhibits a step-like isotherm\nis studied as the sorbent of choice. The MOF has a high heat of adsorption,\nand due to the steep isotherm, there can be considerable local temperature\nchange upon adsorption/desorption that can considerably affect its\nperformance. To obtain particle level resolution of the transport\nvariables and resulting performance, a particle scale model is developed\nand coupled with a model of the bulk-scale leading to a multiscale\nmodel of the radial flow bed. A multiscale model of an axial flow\nbed is also developed for comparing the model results with the experimental\nbreakthrough data for the functionalized metal–organic framework.\nCo-flow and counter-current flow configurations are modeled. An economic\nmodel is developed. Operating conditions are optimized. Considering\nthe utility prices for 2017, it is observed that the optimal counter-current\nand cocurrent RFFBs have 19 and 22.6% lower equivalent annual operating\ncost (EAOC), respectively, compared to that for the axial flow beds\nand 13.1 and 17% lower EAOC, respectively, compared to that for the\nmonoethanolamine (MEA)-based capture. For the 2023 utility price,\noptimal counter- and cocurrent RFFBs have 40.9 and 44.8% lower EAOC,\nrespectively, compared to the MEA-based capture. It is observed that\nthe cocurrent radial flow bed with the flue gas entering at the outer\nannulus has the best economic performance for this metal–organic\nframework compared to the counter-current radial flow beds, axial\nflow beds, and the MEA-based capture.